The invention generally relates to the area of telephonic data transmission facilities. More particularly, the present invention concerns methods and apparatuses for ensuring that a signal transmitted on a twisted pair line will be received at a remote system with sufficient power.
Telecommunications modem systems, of which pair gain systems are a specific example, experience electrical signal power loss between transmission and reception facilities which are typically several kilometers apart. Copper wire, the typical medium for signal transmission on such systems, is a very good conductor and signal losses over short distances are negligible. However, when used to transmit signals for several kilometers in a telecommunications modem system environment, the signal power loss during transmission on the copper wire is no longer negligible. As a consequence, the span, or total distance from source to receiver is limited.
Furthermore the transmitted signals often pass through one or more line-powered repeater nodes powered by the twisted pair line carrying the transmitted signals. The electronic circuitry within the repeater nodes consumes power and thus the power transmitted from the repeater nodes is less than the input power to the repeater nodes. If a transmission path includes a number of such repeaters, the power consumed becomes substantial and power must be added to the wire in order to achieve the desired span for the line-powered series of repeater nodes.
It is known to add power to the transmitted power from the signal pair signal at a repeater or other type of node. The added power originates from previously installed remote high voltage power sources. Phone companies install these power sources to provide power to existing equipment. The remote power supplies are typically already in existence. Power lines are extended from the existing remote high voltage power sources to repeater nodes where their power is added to the power from the signaling pair. Special circuitry must be included in the repeater nodes to facilitate attachment of the power supply lines from the remote power source to the repeater nodes.
The limitations on potential span present a significant problem to phone companies serving remotely located customers. The density of remote power sources is greatest in areas of high population density. In areas of high population density, remote high voltage power supplies are likely to be found at convenient locations so that power can be supplied at a repeater node. However, in sparsely populated areas, finding a conveniently located power supply is less likely.
Yet another potential problem is the added cost to enable adding the power boosting lines at a repeater node. Hardware capability would have to be provided for all repeaters unless the manufacturer was willing to support two distinct hardware configurations, one configuration that enabled and another that did not enable attaching the supplemental power lines at the repeater nodes. In this case, nodes would be swapped out if the customer decides to add a supplemental power line pair.
The present invention improves the quality and accuracy of data transmissions in order to overcome some, if not all, of the problems encountered when attempting to provide additional power to telecommunications modem system lines. A power combiner provides an interface between a remote high voltage power source and twisted pair lines connecting a transmitter and receiver in a telecommunications modem system. The combiner comprises a first interface to the high voltage power source. The first interface is communicatively coupled to a low pass filter interposed between the first interface and an attached telecommunications modem system twisted pair line. The low pass filter is constructed such that the data signal transmitted on the telecommunications modem system line does not pass to the first interface. A second interface connects the. low pass filter to the telecommunications modem system twisted pair line.
In accordance with a more particular aspect of certain embodiments of the present invention, the first interface comprises a diode bridge. The diode bridge automatically configures the connections between the power supply lines and the combiner. The diode bridge ensures that regardless of which power supply input terminals of the combiner the positive and negative voltage lines are connected, the internal path of current through the combiner will be configured so that the power supply lines are properly connected to the positive and negative voltage inputs to the low pass filter. This circuit eliminates the possibility that a technician will incorrectly attach positive and negative input lines of the low-pass filter to a remote power source.
In accordance with another aspect of certain embodiments of the present invention, switching circuitry within the second interface automatically configures the line connections between the low pass filters and the telecommunications modem system twisted pair lines. As a result, the positive and negative voltage lines from low pass filter are properly connected to the telecommunications modem system regardless of how a technician connects the external terminals of the combiner to the telecommunications modem lines. Thus, the two self-configuring circuits enable a person to splice the combiner circuit into a telecommunications modem line with knowledge only of which terminals are connected to. the power supply and which ones are connected to the telecommunications modem line. The person need not know the polarity of either the remote power twisted pair or the signaling twisted pair since the combiner apparatus will automatically configure its internal connections to establish the proper line polarities.